36 



ASTEROIDEA. 



out, but appears to have had a framework composed of closely-set polygonal ossicula. 

 Around it are arranged the rays, equidistant from each other, like so many spokes of a 

 wheel. Their average length is one inch and one-twelfth, and their breadth towards the 

 base, four-twelfths. They are regularly lanceolate. Their under surfaces are exposed on 

 the slab, and are composed of thick, transversely oblong plates, slightly overlapping each 

 other in scale-like fashion, and ranged in four longitudinal rows, two on each side of a 

 central or ambulacral groove, which is itself towards the extremity, in some instances, 

 partially filled up by small polygonal intervening plates. Of the two rows of border 

 plates on each side of the groove, the inner series is formed of oblong obscurely hexagonal 

 ones, with traces of punctations and grooves on the surfaces, as if for spines. The ray 

 that is most perfect exhibits twenty-five plates in each row. The outer series consists of 

 sub-orbicular or obscurely polygonal plates, which, like the inner ones, are gently convex 

 on their surfaces. The upjier surface of the ray, and probably of the body, was composed 

 of numerous small, polygonal, nearly flat ossicula, closely set, and of various sizes.'' 



This remarkable fossil was associated with several species of Crinoids, both perfect 

 specimens and in fragments, but the most careful search has never brought to light another 

 specimen of Lepidaster. 



Besides the species above enumerated, other Palaeozoic Asteroidea have been mentioned 

 by the following authors. 



Hisinger^ described and figured Palasteritia antiqua from Ludlow rocks at Mount 

 Hoburg, Gothland, Sweden. 



Professor James Hall ' has figured and described 'Palcaadcr matutina from the Lower 

 vSilurian rocks of the State of New York. 



Mr. Troost'^ has figured and described Aslerias antiqtia from Silurian rocks in the State 

 of Tennessee, and the author alludes to five other undescribed species, from beds of the same 

 formation. 



Mr. Locke' has recorded the same species, Asterias antiqua, from the Lower Silurian 

 rocks of the State of Pennsylvania. 



Johannes Midler^ has described as Asterias JRhenana, a star-fish with marginal plates, 

 obtained from Devonian Sandstone at Coblenz. 



M. Thorent^ has figured and described a Palaeozoic asteriad, under the name 

 Asterias constellata, collected from Dumont's " Terrain anthraxifere," in France, in the 

 department of I'Aisne ; this star-fish belongs to the same group of forms which Forbes, 



' Hisinger, • Letliea Suecica,' t. Ixxxix, (. 2t;, fig. 6. 



- Hall, ' Palfeoutology of New York,' vol. i, t. 2[t, fig. 5. 



Troost, 'Transact. Geological Soc. Pennsylvania,' vol. i, p. 232, t. 10, fig. 9. 

 1 Locke, 'Free. .'Vc. N. S. Phil.,' vol. iii. 



Miiller, ' V'erh. Naturli. ver. fiir Rlieinl. und Westpbl. Jahrg.,' xii, 1855. 

 " Thorent, 'Memoires Soc. Geol. do France,' tome iii, tab. 22, fig. 7. 



